Added javax.activation dependency for Java 9+ support and added maven enforcer plugin (#327).

pom.xml

@@ -60,7 +60,7 @@
 	</scm>
 
 	<build>
-		<defaultGoal>package</defaultGoal>		
+		<defaultGoal>package</defaultGoal>
 		<plugins>
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
@@ -99,7 +99,7 @@
 				</executions>
 			</plugin>
 
-            <plugin>
+			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-gpg-plugin</artifactId>
 				<version>1.6</version>
@@ -132,6 +132,9 @@
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-javadoc-plugin</artifactId>
 				<version>3.0.0</version>
+				<configuration>
+					<source>8</source>
+				</configuration>
 				<executions>
 					<execution>
 						<id>attach-javadocs</id>
@@ -145,7 +148,7 @@
 			<plugin>
 				<groupId>org.jacoco</groupId>
 				<artifactId>jacoco-maven-plugin</artifactId>
-				<version>0.8.0</version>
+				<version>0.8.3</version>
 				<executions>
 					<execution>
 						<id>default-prepare-agent</id>
@@ -188,17 +191,49 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-surefire-plugin</artifactId>
-				<version>2.19.1</version>
+				<version>2.22.0</version>
 				<configuration>
 					<systemPropertyVariables>
 						<jacoco-agent.destfile>target/jacoco.exec</jacoco-agent.destfile>
 					</systemPropertyVariables>
 				</configuration>
 			</plugin>
+
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-enforcer-plugin</artifactId>
+				<version>3.0.0-M2</version>
+				<configuration>
+					<rules>
+						<enforceBytecodeVersion>
+							<maxJdkVersion>1.8</maxJdkVersion> 
+							<ignoreClasses>
+								<ignoreClass>module-info</ignoreClass>
+							</ignoreClasses>
+						</enforceBytecodeVersion>
+					</rules>
+				</configuration>
+				<executions>
+					<execution>
+						<id>enforce-bytecode-version</id>
+						<goals>
+							<goal>enforce</goal>
+						</goals>
+					</execution>
+				</executions>
+				<dependencies>
+					<dependency>
+						<groupId>org.codehaus.mojo</groupId>
+						<artifactId>extra-enforcer-rules</artifactId>
+						<version>1.2</version>
+					</dependency>
+				</dependencies>
+			</plugin>
+
 		</plugins>
 
 		<pluginManagement>
-			<plugins>			
+			<plugins>
 				<plugin>
 					<groupId>se.bjurr.gitchangelog</groupId>
 					<artifactId>git-changelog-maven-plugin</artifactId>
@@ -217,10 +252,18 @@
 				</plugin>
 			</plugins>
 		</pluginManagement>
+
 	</build>
 
 	<dependencies>
 
+		<!-- javax.activation is present for Java 9+ compatibility -->
+		<dependency>
+			<groupId>com.sun.activation</groupId>
+			<artifactId>javax.activation</artifactId>
+			<version>1.2.0</version>
+		</dependency>
+
 		<dependency>
 			<groupId>com.fasterxml.jackson.jaxrs</groupId>
 			<artifactId>jackson-jaxrs-json-provider</artifactId>
@@ -276,6 +319,7 @@
 			<version>${systemRules.version}</version>
 			<scope>test</scope>
 		</dependency>
+
 	</dependencies>
 
 </project>